A solution of the DGLAP equation for gluon at low x

We obtain a solution of the DGLAP equation for the gluon at low x first by expanding the gluon in a Taylor series and then using the method of characteristics. We test its validity by comparing it with that of Glück, Reya and Vogt. The convergence criteria of the approximation used are also discussed. We also calculate εF ₂(x,Q)²/ε In Q ² using its approximate relations with the gluon distribution at low x. The predictions are then compared with the HERA data.     

CRYPTATES XIX. Ligands polyaza-polyoxa-macrobicycliques: Synthèse et complexes métalliques

Polyaza-polyoxa macrobicyclic ligands: its synthesis and metal complexes. The synthesis of the polyaza-polyoxa macrobicyclic ligands 1–4 is described. They form complexes with a variety of metal cations, transition metal cations as well as alkali and alkaline-earth cations. These complexes may be formulated as cation inclusion complexes, cryptates, in which the cation is contained in the intramolecular cavity. The properties of the complexes are described. An especially interesting feature is that these ligands, polymines of macrobicyclic topology, provide a means of trapping transition metal cations inside a molecular cavity; thus they impose coordination geometries and may modify the spectral and redox properties of the cations.     

Effect of alkali ions (Na+, K+) on the solvent extraction of uranium(VI) with a di-carboxylated calix[4] arene

The solvent extraction of uranium(VI) with a di-carboxylated calix[4]arne (LH₂) in chloroform and 1,2-dichloroethane has been studied in the presence or absence of alkali ions (M=Na⁺,K⁺). For UO ₂ ²⁺ when studied alone, a 12 (metal: ligand) extracted species is evidenced, with a rather low associated extraction equilibrium constant. The efficiency of extraction increases drastically in the presence of alkali ions, due to the formation of heteronuclear complexes. In all cases, the extracted species are found to be both 122 and 112 (UO ₂ ²⁺ MLH₂) mixed complexes, except in chloroform with K⁺, where only the latter is formed. In the case of Na⁺, mass spectrometry spectra confirm the existence of both homo and heteronuclear complexes as determined in the extraction studies.     

Synthesen in der Carotinoid-Reihe. 22. Mitteilung. Totalsynthese von Rhodoxanthin

The total synthesis of rhodoxanthin according to the scheme C₁₄ + C₁₂ + C₁₄ is reported.     

Advances on the Determination of the Astatine Pourbaix Diagram: Predomination of AtO(OH)2− over At− in Basic Conditions

It is generally assumed that astatide (At^?) is the predominant astatine species in basic aqueous media. This assumption is questioned in non‐complexing and non‐reductive aqueous solutions by means of high‐pressure anion‐exchange chromatography. Contrary to what is usually believed, astatide is found to be a minor species at pH=11. A different species, which also bears a single negative charge, becomes predominant when the pH is increased beyond 7. Using competition experiments, an equilibrium constant value of 10^?6.9 has been determined for the formation of this species from AtO(OH) with the exchange of one proton. The identification of this species, AtO(OH)₂^?, is achieved through relativistic quantum mechanical calculations, which rule out the significant formation of the AtO₂^? species, while leading to a hydrolysis constant of AtO(OH) in excellent agreement with experiment when the AtO(OH)₂^? species is considered. Beyond the completion of the Pourbaix diagram of astatine, this new information is of interest for the development of ²¹¹At radiolabeling protocols.     

Synthese und Reaktionen des 5-[p-(Dimethylamino)phenyl]-2,2-dimethyl-4-phenyl-3-oxazolins

Synthesis and Reactions of 5-[p-(Dimethylamino)phenyl]-2,2-dimethyl-4-phenyl-3-oxazoline The title compound 8 has been synthesized in a one-pot reaction of 4′-(dimethylamino)benzoin ( 4 ) with 2-propanone and NH₃. The preparation of the intermediate 4 from 3 is the first example of an acid-catalyzed transformation of the stable benzoin 3 into the corresponding less stable benzoin 4 . Structures and yields of various by-products occurring under different reaction conditions during the synthesis of 8 from 4 are given. The O-atom of the 3-oxazoline ring in 8 could be replaced by S from P₂S₅ yielding the 3-thiazoline 14 . Separation of the enantiomers of the racemate 8 could only be performed by transforming them into the trimethylanilinium salts 8b and 8c of (−)- and (+)-10-camphorsulfonic acid, respectively. Solid NaOAc in boiling toluene caused the precipitation of the 10-camphorsulfonic acids from the quaternary ammonium salts as sodium salts and the removing of the third methyl group from the quaternary ammonium salts as AcOMe to give the enantiomers (−)-(5S)- 8 and (+)-(5R)- 8 . Their absolute configurations are deduced from an X-ray analysis of 8b .     

A short and efficient synthesis of the NMDA glycine site antagonist: (3R,4R)-3-amino-1-hydroxy-4-methyl pyrrolidin-2-one (L-687,414)

A short and efficient synthesis of the NMDA glycine site antagonist: (3R,4R)-3-amino-1-hydroxy-4-methyl pyrrolidin-2-one (L-687,414) is described.